1. Field of the Invention
The present invention relates to an apparatus for driving a stepping motor in a micro step manner by using a pulse width modulation (PWM) control signal.
2. Description of the Related Art
In a prior art apparatus for driving a stepping motor in a micro step manner by a PWM control signal generated based on a sense voltage, including a sense resistor for generating the sense voltage, a driving current path including the sense resistor and the stepping motor is provided and is operated so that a driving current flows through the stepping motor, when the PWM control signal is activated. A regenerative current path including the sense resistor and the stepping motor is provided and is operated so that a regenerative current flows through the stepping motor, when the PWM control signal is not activated. This will be explained later in detail.
In the above-mentioned prior art apparatus, however, a resistance of the regenerative current path is generally small. As a result, a time constant of the regenerative current path is large, and accordingly, a reduction rate of the regenerative current is small. Therefore, the sense voltage of the sense resistor cannot follow the change of the step reference voltage signal of a step reference voltage generating circuit. As a result, the drive current is distorted. Particularly, the magnitude of the drive current on the decrease cannot be decreased in a sine wave form, which creates vibration and noise in the motor.